In underground mining, in order to keep cavities for the secure arrangement of the mining machines in the so-called working face open, variable-height shield supports or shield support frames, which generally have two floor skids, a link mechanism with generally four links employed as a lemniscate system, a gob shield, and a roof cap articulately connected to the gob shield, are used. Through the extension of hydraulic cylinders, which support the roof cap with respect to the floor skids, the roof cap is pressed against the so-called roof, while the gob shield, at the rear or on the packing side of the mining plant, prevents the rock from caving in.
Numerous property right applications relate to the structure of the shield support, the designs of the floor skid and the structural design of the roof cap. The gob shield is here generally regarded only as a connecting link between the link mechanism and the roof cap and has been constructed and produced in exactly the same way for years.